Refrigeration systems are used in many applications for heating and cooling a controlled environment, including a cargo box on a transport truck, train, ship or plane. The refrigeration system has many components including a condenser, an evaporator, and a compressor. Before transporting the cargo, it is desirable to determine whether the refrigeration system is in an operational condition.
There have been some attempts to use a pretrip device to determine the operational condition of the refrigeration system prior to transportation. One such device to Hanson et al., U.S. Pat. No. 5,172,561, includes a pretrip device which determines the operational condition of the refrigeration system as a function of temperature change. However, this pretrip device always runs the same pretrip routine independent of whether environmental conditions call for the refrigeration system to operate in a heating mode or a cooling mode. As a result, the refrigeration system is not properly adjusted prior to beginning the operational testing of the refrigeration system, which results in false alarms and various other faulty results.
When an alarm is signaled, the refrigeration system must be taken out of service and be inspected for problems, which takes time and costs money. When the alarm is false, it takes longer to service because there are no identifiable problems.